Chemical conversion treatment agent, coating pre-treatment method, and metal member

ABSTRACT

Provided is a chemical conversion treatment agent that has a small impact on the environment and can ensure good post-coating corrosion resistance regardless of the target of treatment. A chemical conversion treatment agent including: at least one type (A) of element selected from the group consisting of zirconium, titanium, and hafnium; at least one type (B) of substance selected from the group consisting of amino group-including silane coupling agents, hydrolysates thereof, and polymers thereof; fluorine (C); and a cationic urethane resin (D). Preferably, the content of (A) is 20-10000 mass ppm in total in terms of metals, and the pH is 1.5-6.5.

TECHNICAL FIELD

The present invention relates to a chemical conversion treatment agent,a pre-coating treatment method, and a metal member.

BACKGROUND ART

Chemical conversion treatment is usually performed for the purpose ofimproving properties such as corrosion resistance and coatingadhesiveness when a surface of a metal material is subjected to cationelectrodeposition coating, powder coating, or the like. Chromatetreatment is commonly used for chemical conversion in view of itscapability of further improving adhesion and corrosion resistance of acoated film. In recent years, the hazardous properties of chromium,however, have been noted, and thus there have been demands fordeveloping a chemical conversion treatment agent which does not containchromium. As such chemical conversion, widely performed is zincphosphate treatment.

However, zinc phosphate-based treatment agents contain highconcentrations of metal ions and acids, and are highly reactive. Thismay result in poor waste-treatment economy and poor workability.Further, when a metal surface is treated with a zinc phosphate-basedtreatment agent, water-insoluble salts may be generated and deposited asprecipitates. These precipitates are generally referred to sludge. Theremoval and disposal of such sludge may add undesirable costs and otherproblems. Further, phosphate ions may be responsible for increasedenvironmental burden due to eutrophication, and may require additionalefforts for waste treatment. Therefore, use of phosphate ions ispreferably avoided. Moreover, the treatment of a metal surface with azinc phosphate-based treatment agent requires surface conditioning.This, disadvantageously, may result in a prolonged process.

As metal-surface treatment agent other than such a zinc phosphate-basedtreatment agent or a chromate chemical conversion treatment agent, knownis a metal-surface treatment agent including a zirconium compound. Sucha metal-surface treatment agent including a zirconium compound has asuperior property as compared with a zinc phosphate-based chemicalconversion treatment agent as described above in that the generation ofsludge can be prevented.

Unfortunately, a chemical conversion film obtained by a metal-surfacetreatment agent including a zirconium compound shows poor adhesiveness,in particular with a coated film obtained by cation electrodepositioncoating, and is less often used as a pre-treatment step of cationelectrodeposition coating. In such a metal-surface treatment agentincluding a zirconium compound, a component such as phosphate ions maybe used in combination for improving adhesiveness and corrosionresistance. However, when phosphate ions are used in combination, theaforementioned problems such as eutrophication may occur. Moreover, aniron-based base material treated with such a metal-surface treatmentagent may have a problem in that neither sufficient coating adhesivenessnor post-coating corrosion resistance can be obtained.

A non-chromate metal-surface treatment agent is also known whichincludes a zirconium compound and an amino group-containing silanecoupling agent. However, surface treatment with such a non-chromatemetal-surface treatment agent as an application-type treatment agentused in the field of so-called coil coating is not comparable withpost-treatment water-washing. Further, such a non-chromate metal-surfacetreatment agent is not intended for a target workpiece having acomplicated shape.

Furthermore, for an article, such as an automobile body and parts,composed of a metal material such as iron, zinc, and aluminum, theentire metal surface may need to be treated in a single treatment.Accordingly, a pre-coating treatment method is desired to be developed,by which chemical conversion can be performed without causing anyproblem even in such a case. Meanwhile, a pre-coating treatment methodis also desired to be developed, by which chemical conversion can beperformed without causing the aforementioned problems even in coatingother than cation electrodeposition coating using a powder coatingmaterial, a solvent coating material, a water-based paint, and the like.

In an attempt to solve the above problems, a pre-coating treatmentmethod is known, the method involving treating a target workpiece with achemical conversion treatment agent including at least one selected fromthe group consisting of zirconium, titanium, and hafnium; fluorine; andat least one selected from the group consisting of an aminogroup-containing silane coupling agent, hydrolysates thereof, polymersthereof to form a chemical conversion film (for example, see PatentDocument 1 below).

The above pre-coating treatment method is compatible with any commoncoating methods, and can provide similar adhesiveness and post-coatingcorrosion resistance as a case where a zinc phosphate-based chemicalconversion treatment agent is used. However, post-coating corrosionresistance obtained was less than satisfactory, depending on a treatmenttarget and applications thereof.

Patent Document 1: Japanese Unexamined Patent Application, PublicationNo. 2004-218070

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

The present invention is made in view of the above circumstances. Anobject of the present invention is to provide a chemical conversiontreatment agent which may cause less environmental burden, and canensure good post-coating corrosion resistance regardless of treatmenttargets.

Means for Solving the Problems

The present invention relates to a chemical conversion treatment agentincluding at least one (A) selected from the group consisting ofzirconium, titanium, and hafnium; at least one (B) selected from thegroup consisting of an amino group-containing silane coupling agent,hydrolysates thereof, and polymers thereof; fluorine (C); and a cationicurethane resin (D).

Further, it is preferred that the total content of (A) is 20 to 10000ppm by mass in terms of metal, and pH is 1.5 to 6.5.

Moreover, it is preferred that the total content of (B) is 5 to 5000 ppmby mass in the solid content concentration, and the content of (D) is 5to 5000 ppm by mass in the solid content concentration, and, the solidcontent mass ratio ((B)/(D)) of (B) to (D) is 0.0002 to 5000.

Moreover, it is preferred to further contain at least one adhesivenessand corrosion resistance-conferring agent selected from the groupconsisting of magnesium ions, zinc ions, calcium ions, aluminum ions,gallium ions, indium ions, and copper ions.

The present invention also relates to a pre-coating treatment methodincluding treating a target workpiece with the above chemical conversiontreatment agent.

Further, the present invention relates to a metal member treated by theabove pre-coating treatment method.

Effects of the Invention

The present invention can provide a chemical conversion treatment agentwhich may cause less environmental burden, and can ensure goodpost-coating corrosion resistance regardless of treatment targets.

PREFERRED MODE FOR CARRYING OUT THE INVENTION

Below, the embodiments of the present invention will be described. It isnoted that the present invention shall not be limited to the followingembodiments.

<Chemical Conversion Treatment Agent>

A chemical conversion treatment agent according to the presentembodiment can form a chemical conversion film on a metal surface as atarget workpiece, and confer preferred post-coating corrosion resistanceon the metal surface. There is no particular limitation for a metal as atarget workpiece, but any metals such as iron, zinc, and aluminum may beused. Further, the chemical conversion treatment agent according to thepresent embodiment is preferably used in particular for iron-basedhighly high tension steel sheets and hot-rolled steel sheets. Such aniron-based highly high tension steel sheets and hot-rolled steel sheetsare widely used in suspension related parts of automobiles and the like.However, a uniform chemical conversion film may be difficult to beformed on a surface thereof due to an oxide film which may be formed onthe surface. The chemical conversion treatment agent according to thepresent embodiment, which is substantially free of phosphate ions andhazardous heavy metal ions, can form a uniform chemical conversion filmeven on the surfaces of a highly high tension steel sheet and ahot-rolled steel sheet. This can ensure good post-coating corrosionresistance of a target workpiece.

The chemical conversion treatment agent according to the presentembodiment includes at least one (A) selected from the group consistingof zirconium, titanium, and hafnium; at least one (B) selected from thegroup consisting of an amino group-containing silane coupling agent,hydrolysates thereof, and polymers thereof; and fluorine (C); and acationic urethane resin (D).

The at least one (A) selected from the group consisting of zirconium,titanium, and hafnium corresponds to a component for forming a chemicalconversion film. Formation of a chemical conversion film including atleast one selected from the group consisting of zirconium, titanium, andhafnium on a base material can improve corrosion resistance and abrasionresistance of the base material, and further can enhance adhesivenesswith a coated film.

For example, when a metal base material is surface treated with achemical conversion treatment agent containing zirconium, metal ionswhich are eluted into the chemical conversion treatment agent due to adissolution reaction of metal may extract fluorine from ZrF62-, or aninterface pH may be increased. These may result in generation ofhydroxides or oxides of zirconium. These hydroxides or oxides ofzirconium are thought to be deposited on a surface of a base material.As described above, the chemical conversion treatment agent according tothe present embodiment, which is a reactive chemical conversiontreatment agent, can be used even for dipping treatment of a targetworkpiece having a complicated shape. Moreover, surface treatmentperformed with the above chemical conversion treatment agent can producea chemical conversion film adhering firmly on a target workpiece byvirtue of a chemical reaction. This also can allow post-treatmentwater-washing to be performed.

There is no particular limitation for a source of the above zirconium,but examples of the source include, for example, alkali metalfluorozirconate such as K2ZrF6; fluorozirconate such as (NH4)2ZrF6;soluble fluorozirconate such as fluorozirconate acid such as H2ZrF6;zirconium fluoride; zirconium oxide; and the like.

There is no particular limitation for a source of the above titanium,but examples of the source include, for example, fluorotitanate such asalkali metal fluorotitanate, (NH4)2TiF6; soluble fluorotitanate such asfluorotitanate acid such as H2TiF6; titanium fluoride; titanium oxide;and the like.

There is no particular limitation for a source of the above hafnium, butexamples of the source include, for example, fluorohafnate acid such asH2HfF6; hafnium fluoride; and the like. A source of the at least oneselected from the group consisting of zirconium, titanium, and hafniumis preferably a compound having at least one selected from the groupconsisting of ZrF62-, TiF62-, and HfF62- in view of high film-formingcapability.

The total content of the at least one selected from the group consistingof zirconium, titanium, and hafnium included in the chemical conversiontreatment agent according to the present embodiment is preferably withina range between a lower limit of 20 ppm by mass and an upper limit of10000 ppm by mass in terms of metal. When the amount is less than 20 ppmby mass, the resulting chemical conversion film may have insufficientperformance. On the other hand an amount of more than 10000 ppm by masscan not provide additional effects, and is thus economicallydisadvantageous. The above lower limit is more preferably 50 ppm bymass, and even more preferably 100 ppm by mass. The above upper limit ismore preferably 2000 ppm by mass, and even more preferably 500 ppm bymass.

The at least one (B) selected from the group consisting of an aminogroup-containing silane coupling agent, hydrolysates thereof, andpolymers thereof is a compound having at least one amino group in amolecule thereof and also having a siloxane bond. The above at least one(B) selected from the group consisting of an amino group-containingsilane coupling agent, hydrolysates thereof, and polymers thereof caninteract with both a chemical conversion film and a coated film. Thiscan improve adhesiveness between them.

This effect can be obtained presumably because a group which can undergohydrolysis to produce silanol is hydrolyzed and adsorbed on a surface ofa metal base material via hydrogen bond, and an amino group can act toenhance adhesiveness between a chemical conversion film and a metal basematerial. As described above, the at least one (B) selected from thegroup consisting of an amino group-containing silane coupling agent,hydrolysates thereof, and polymers thereof is thought to act on both ametal base material and a coated film to show an effect of improvingmutual adhesiveness.

There is no particular limitation for the above amino group-containingsilane coupling agent, but examples thereof can include, for example,publicly known silane coupling agents such asN-2(aminoethyl)3-aminopropylmethyldimethoxysilane,N-2(aminoethyl)3-aminopropyltrimethoxysilane,N-2(aminoethyl)3-aminopropyltriethoxysilane,3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane,3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine,N-phenyl-3-aminopropyltrimethoxysilane,N,N-bis[(3-(trimethoxysilyl)propyl)]ethylenediamine, and the like.Commercially available amino group-containing silane coupling agentsKBM-602, KBM-603, KBE-603, KBM-903, KBE-9103, KBM-573 (Shin-EtsuChemical Co., Ltd.), XS1003 (Chisso Corp.), and the like may also beused.

Hydrolysates of the above amino group-containing silane coupling agentcan be prepared by conventionally known methods, for example, by amethod including dissolving the above amino group-containing silanecoupling agent in ion-exchanged water, and adjusting it to be acidicwith any acid, and the like. As a hydrolysate of the above aminogroup-containing silane coupling agent, a commercially available productsuch as KBP-90 (Shin-Etsu Chemical Co., Ltd., Active ingredient: 32%)may also be used.

There is no particular limitation for a polymer of the above aminogroup-containing silane coupling agent, but examples thereof caninclude, for example, commercially available products such as Sila-AceS-330 (γ-aminopropyltriethoxysilane; Chisso Corp.), Sila-Ace S-320(N-(2-aminoethyl)-3-aminopropyltrimethoxysilane; Chisso Corp.).

The total blending amount of the at least one (B) selected from thegroup consisting of an amino group-containing silane coupling agent,hydrolysates thereof, and polymers thereof in the chemical conversiontreatment agent according to the present embodiment is preferably withina range between a lower limit of 5 ppm by mass and an upper limit of5000 ppm by mass in terms of the solid content concentration. An amountof less than 5 ppm by mass can not provide sufficient coatingadhesiveness. An amount of more than 5000 ppm by mass can not provideadditional effects, and is thus economically disadvantageous. The abovelower limit is more preferably 10 ppm by mass, and even more preferably50 ppm by mass. The above upper limit is more preferably 1000 ppm bymass, and even more preferably 500 ppm by mass.

Fluorine (C) can serve as an etching agent for a base material. There isno particular limitation for a source of fluorine (C), but examples ofthe source can include, for example, fluorides such as hydrofluoricacid, ammonium fluoride, fluoroboric acid, ammonium hydrogen fluoride,sodium fluoride, and sodium hydrogenfluoride. Further, complex fluoridesinclude, for example, hexafluorosilicate, and specific examples thereofcan include hydrosilicofluoric acid, zinc hydrofluorosilicate, manganesehydrofluorosilicate, magnesium hydrofluorosilicate, nickelhydrofluorosilicate, iron hydrofluorosilicate, calciumhydrofluorosilicate, and the like.

The cationic urethane resin (D) will form a uniform chemical conversionfilm on a metal surface as a target workpiece. The cationic urethaneresin (D) has a cationic functional group. Cationic functional groupsinclude, for example, an amino group, an ammonium group, a methylaminogroup, an ethylamino group, a dimethylamino group, a diethylamino group,a trimethylamino group, a triethylamino group, and the like. Amongthese, prepared is a quaternary ammonium group. Moreover, there is noparticular limitation for a polyol, isocyanate components of a urethaneresin of the cationic urethane resin (D), and a method ofpolymerization, but conventionally known components and methods may beused. As the cationic urethane resin (D), the followings may be used:for example, commercially available products such as F2667D (DKS Co.Ltd., Effective concentration: 25%), Superflex 620 (DKS Co. Ltd.,Effective concentration: 30%), and Superflex 650 (DKS Co. Ltd.,Effective concentration: 26%).

Inclusion of the cationic urethane resin (D) alone in a chemicalconversion treatment agent can not provide preferred effects such aspost-coating corrosion resistance. However, when it is included in achemical conversion treatment agent in combination with the at least one(B) selected from the group consisting of an amino group-containingsilane coupling agent, hydrolysates thereof, and polymers thereof, auniform chemical conversion film can be formed on a surface of a metalsurface as a target workpiece, ensuring a preferred post-coatinganticorrosion properties of that metal member as a target workpiece.Further, the cationic urethane resin (D) does not undergo a competingreaction with the at least one (B) selected from the group consisting ofan amino group-containing silane coupling agent, hydrolysates thereof,and polymers thereof, and thus may be preferably used without inhibitingthe functionality of the amino group-containing silane coupling agent,hydrolysates thereof, and polymers thereof (B).

The blending amount of the cationic urethane resin (D) in the chemicalconversion treatment agent according to the present embodiment ispreferably within a range between a lower limit of 5 ppm by mass and anupper limit of 5000 ppm by mass in terms of the solid contentconcentration. An amount of less than 5 ppm by mass can not providesufficient coating adhesiveness. An amount of more than 5000 ppm by masscan not provide additional effects, and is thus economicallydisadvantageous. The above lower limit is more preferably 10 ppm bymass, and even more preferably 50 ppm by mass. The above upper limit ismore preferably 1000 ppm by mass, and even more preferably 500 ppm bymass.

In the chemical conversion treatment agent according to the presentembodiment, the mass ratio ((B)/(D)) of the at least one (B) selectedfrom the group consisting of an amino group-containing silane couplingagent, hydrolysates thereof, and polymers thereof to the cationicurethane resin (D) is preferably 0.0002 to 5000. A mass ratio ((B)/(D))falling within the above range can achieve preferred post-coatingcorrosion resistance of a target workpiece on which a chemicalconversion film is formed. The mass ratio ((B)/(D)) is more preferably0.01 to 100, and even more preferably 0.5 to 2.

Preferably, the chemical conversion treatment agent according to thepresent embodiment is substantially free of phosphate ions. The phrase“substantially free of phosphate ions” means that phosphate ions may beincluded in an amount such that they do not function as a component of achemical conversion treatment agent. The chemical conversion treatmentagent used in the present embodiment is substantially free of phosphateions. Therefore, essentially no phosphorus is used which is potentiallyresponsible for increased environmental burden. Further, generation ofsludge such as iron phosphate and zinc phosphate can be prevented, whichotherwise may be generated when a zinc phosphate-based treatment agentis used.

The chemical conversion treatment agent according to the presentembodiment preferably has a pH falling within a range between a lowerlimit of 1.5 and an upper limit of 6.5. A pH of lower than 1.5 mayresult in excessive etching, and a sufficient film can not be formed. ApH of more than 6.5 may result in insufficient etching, and can notprovide a good film. The above lower limit is more preferably 2.0, andthe above upper limit is more preferably 5.5. The above lower limit iseven more preferably 2.5, and the above upper limit is even morepreferably 5.0. In order to adjust a pH of the chemical conversiontreatment agent according to the present embodiment, an acidic compoundsuch as nitric acid and sulfuric acid and a basic compound such assodium hydroxide, potassium hydroxide, and ammonia may be used.

Preferably, the chemical conversion treatment agent according to thepresent embodiment further includes at least one selected from the groupconsisting of magnesium ions, zinc ions, calcium ions, aluminum ions,gallium ions, indium ions, and copper ions as an adhesiveness andcorrosion resistance-conferring agent. Inclusion of the aboveadhesiveness and corrosion resistance-conferring agent can provide achemical conversion film having better adhesiveness and corrosionresistance.

The content of the above at least one selected from the group consistingof magnesium ions, zinc ions, calcium ions, aluminum ions, gallium ions,indium ions, and copper ions is preferably within a range between alower limit of 1 ppm by mass and an upper limit of 5000 ppm by mass.When the above content is less than the above lower limit, sufficienteffects can not be obtained. This is not preferred. When the abovecontent is more than the above upper limit, additional effects can notbe obtained. This is economically disadvantageous, and may also decreasepost-coating adhesiveness. The above lower limit is more preferably 25ppm by mass, and the above upper limit is more preferably 3000 ppm bymass.

The above chemical conversion treatment agent may be used in combinationwith any component in addition to the above components, if needed.Components which can be used can include silica and the like. It ispossible to increase post-coating corrosion resistance by adding such acomponent.

<Pre-Coating Treatment Method>

There is no particular limitation for chemical conversion in thepre-coating treatment method according to the present embodiment, but itmay be performed by contacting a chemical conversion treatment agentwith a metal surface under common treatment conditions. The treatmenttemperature upon the above chemical conversion is preferably within arange between a lower limit of 20° C. and an upper limit of 70° C. Theabove lower limit is more preferably 30° C., and the above upper limitis more preferably 50° C. The chemical conversion time for the abovechemical conversion is preferably within a range between a lower limitof 5 seconds and an upper limit of 1200 seconds. The above lower limitis more preferably 30 seconds, and the above upper limit is morepreferably 120 seconds. There is no particular limitation for a methodof conversion treatment, but examples thereof can include, for example,the dipping method, the spray method, the roll coating method, and thelike.

In the pre-coating treatment method according to the present embodiment,it is preferred that a metal surface may be subjected to degreasingtreatment, post-degreasing water-washing treatment before performing theabove chemical conversion, and subjected to post-chemical conversionwaster-washing treatment after the above chemical conversion. The abovedegreasing treatment may be performed in order to remove oils and stainsadhering on a surface of a base material, and usually performed bydipping treatment at 30 to 55° C. for about several minutes with adegreaser such as phosphorus-free/nitrogen-free degreasing wash liquid.Preliminary degreasing treatment may be performed, if needed, prior todegreasing treatment.

The above post-degreasing water-washing treatment may be conducted byperforming spray treatment using a large amount of wash water once ormore times in order to wash out a degreaser with water after degreasingtreatment. The above post-chemical conversion water-washing treatmentmay be performed once or more times in order to avoid negative effectson adhesiveness, corrosion resistance, and the like after varioussubsequent coatings. In that case, the final water-washing is properlyperformed with pure water. In this post-chemical conversionwater-washing treatment, water washing may be performed by either one ofspray water-washing or dip water-washing or in combination of these.After the above post-chemical conversion water-washing treatment, dryingmay be performed in accordance with a known method, if needed, and thenvarious coatings may be applied.

The pre-coating treatment method according to the present embodimentdoes not require surface conditioning treatment which is required in aconventionally used practical method involving treatment with a zincphosphate-based chemical conversion treatment agent. This enableschemical conversion of a metal base material to be performed in fewersteps.

There is no particular limitation for a metal base material used in thepresent embodiment, but examples thereof can include iron-based basematerials, aluminum-based base materials, and zinc-based base materials.Iron-, aluminum-, and zinc-based base materials mean an iron-based basematerial in which the base material includes iron and/or an alloythereof, an aluminum-based base material in which the base materialincludes aluminum and/or an alloy thereof, and a zinc-based basematerial in which the base material includes zinc and/or an alloythereof, respectively.

Further, the pre-coating treatment method according to the presentembodiment is preferably used in particular for an iron-based highlyhigh tension steel sheet and hot-rolled steel sheet. An oxide filmhaving fine surface unevenness may be formed on a hot-rolled steelsheet, and the oxide film is also of a porous state in which a largenumber of pores are present. For this reason, the surface is verydifficult to be covered with a uniform chemical conversion film. Anununiform chemical conversion film formed on a surface may causedifferent potentials between a coated portion and an uncoated portion,preventing formation of a uniform electrodeposition coated film uponelectrodeposition coating. Consequently, a pre-coating treatment methodusing a conventional chemical conversion treatment agent includingzirconium and others can not ensure post-coating corrosion resistancecomparable to that in a case where a zinc phosphate-based chemicalconversion treatment agent. Similarly, an oxide film having fine surfaceunevenness may also be formed on a highly high tension steel sheet, anda large amount of dissimilar metals may also be included in the highlyhigh tension steel sheet. These may cause the above different potentialsto be more significant, resulting in even less uniform covering with achemical conversion film. Therefore, ensuring post-coating corrosionresistance may be more difficult. However, the pre-coating treatmentmethod according to the present embodiment can form a uniform chemicalconversion film even on an iron-based highly high tension steel sheetand hot-rolled steel sheet, and can ensure post-coating corrosionresistance comparable to that in a case where a phosphate ion-containingchemical conversion treatment agent is used. The mechanism by which suchan effect can be obtained is not clearly understood. Nonetheless, onepossibility is that the cationic urethane resin (D) may preferentiallycover depressed portions and pores of an oxide film through theinteraction between the cationic groups of the cationic urethane resin(D) included in a chemical conversion treatment agent and a surface of asteel sheet.

The film content of a chemical conversion film obtained by thepre-coating treatment method according to the present embodiment ispreferably within a range between a lower limit of 0.1 mg/m2 and anupper limit of 500 mg/m2 in terms of the total amount of metal includedin a chemical conversion treatment agent. An amount of less than 0.1mg/m2 can not provide a uniform chemical conversion film, and is thusnot preferred. An amount of more than 500 mg/m2 can not provideadditional effects, and is thus economically disadvantageous. The abovelower limit is more preferably 5 mg/m2, and the above upper limit ismore preferably 200 mg/m2.

<Metal Member>

A metal base material treated by the above pre-coating treatment methodmay be subjected to laser processing, press working, and the like toobtain a metal member formed and processed depending on variouspurposes. Alternatively, a pre-formed and processed metal member may besubjected to the above pre-coating treatment method. There is noparticular limitation for the applications of a metal member accordingto the present embodiment, but examples of thereof include metal membersof automobiles such as a door, a bonnet, a roof, a hood, a fender, atrunk room, and the like. Further, they also include metal members usedfor motorcycles, buses, bicycles, and the like. A metal member treatedby the pre-coating treatment method according to the present embodimentmay preferably be used in those applications as described above in whicha high level of post-coating corrosion resistance is required in view ofsafely and aesthetics.

There is no particular limitation for coating which can be performed ona metal member treated by the above pre-coating treatment method, butcoating may be performed with a conventionally known coating materialsuch as a cationic electrodeposition coating material, a solvent coatingmaterial, a water-based coating material, and a powder coating material.For example, there is no particular limitation for the above cationicelectrodeposition coating material, but a conventionally known cationicelectrodeposition coating material including an aminated epoxy resin,aminated acrylic resin, a sulfonated epoxy resin, and the like may beapplied. Amount these, a cationic electrodeposition coating materialincluding a resin having a functional group which shows reactivity orcompatibility with an amino group is preferred in order to enhanceadhesiveness between an electrodeposition coated film and a chemicalconversion film, considering that at least one selected from the groupconsisting of an amino group-containing silane coupling agent,hydrolysates thereof, and polymers thereof is blended in a chemicalconversion treatment agent.

The present invention shall not be limited to the above embodiments.Modifications, improvements, and the like can be made within a scope ofthe present invention as long as an effect of the present invention canbe achieved.

EXAMPLES

Next, the present invention will be described in more detail withreference to Examples, but the present invention shall not be limited tothese Examples. It is noted that the term “ppm” as used in Examples andComparative Examples refers to “ppm by mass.”

Example 1

A commercially available cold-rolled steel plate (SPC 270, NipponTestpanel Co., Ltd., 70 mm×150 mm×0.8 mm) as a base material wassubjected to pre-coating treatment under the following conditions.

(1) Pre-Coating Treatment

Degreasing treatment: Dipping treatment was performed at 40° C. with 2%by mass of “Surfcleaner 53” (a degreaser from Nippon Paint SurfChemicals Co., Ltd.). Post-degreasing water-washing treatment: Spraytreatment was performed with tap water for 30 seconds. Chemicalconversion treatment: Zircon hydrofluoric acid and KBM-603(N-2(aminoethyl)3-aminopropyltrimethoxysilane, Effective concentration:100%, Shin-Etsu Chemical Co., Ltd.) as an amino group-containing silanecoupling agent; and F2667D (DKS Co. Ltd., Effective concentration: 25%)as a cationic urethane resin were used to prepare a chemical conversiontreatment agent including zirconium (A) in a concentration of 100 ppm bymass, an amino group-containing silane coupling agent (B) in aconcentration of 100 ppm by mass in terms of the solid content, and acationic urethane resin (D) in a concentration of 100 ppm by mass.Sodium hydroxide was used to adjusted pH to 4. The temperature of thechemical conversion treatment agent was adjusted to 40° C., and a basematerial was dip-treated for 60 seconds. The film amount in the initialstage of the treatment was 13.4 mg/m2.

Post-chemical conversion water-washing treatment: Spray treatment wasperformed with tap water for 30 seconds. Further, spray treatment wasperformed with ion-exchanged water for 10 seconds. Then,electrodeposition coating was performed in a wet condition. Acold-rolled steel sheet after water washing was dried at 80° C. for 5minutes in an electric drying furnace, and then the film amount wasanalyzed as the total amount of metal contained in a chemical conversiontreatment agent with a “ZSX PrimusII” (an X-ray analyzer from RigakuCorporation).

(2) Coating

A cold-rolled steel plate was treated with a chemical conversiontreatment agent at 1 L per m2, and then electrodeposition-coated with“Powernics 310” (a cationic electrodeposition coating material fromNipponpaint Industrial Coatings Co., Ltd.) so as to obtain a dry coatingthickness of 20 μm, and washed with water, and then heated for baking at170° C. for 20 minutes to obtain a test plate.

Examples 2 to 7

Test plates were prepared as in Example 1 except that the metal basematerial was changed to a cold-rolled steel plate (SPC 780 from NipponTestpanel Co., Ltd., 70 mm×150 mm×0.8 mm), hot-rolled steel plates (SPH270, SPH 440, SPH 590 from Nippon Testpanel Co., Ltd., 70 mm×150 mm×0.8mm), a zinc-based plated steel sheet (GA 270 from Nippon Testpanel Co.,Ltd., 70 mm×150 mm×0.8 mm), or a 6000-series aluminum plate (NipponTestpanel Co., Ltd., 70 mm×150 mm×0.8 mm). It is noted that the types ofbase materials shown in Tables 1 and 2 are as follows: SPC representsthe above cold-rolled steel plate; and SPH represents the abovehot-rolled steel plates; and GA represents the above zinc-based platedsteel sheet; and AL represents the above 6000-series aluminum plate.

Examples 8 to 13

Test plates were prepared as in Example 1 except that the above coldrolled steel plate or hot-rolled steel plates were used as a metal basematerial, and the concentrations of the silane coupling agent (B) andthe cationic urethane resin (D) were 1 ppm by mass, 5 ppm by masses, and50 ppm by masses, respectively as shown in Table 1.

Examples 14 and 15

Test plates were prepared as in Example 1 except that the abovehot-rolled steel plates were used as a metal base material, andSuperflex 620 (DKS Co. Ltd., Effective concentration: 30%) or Superflex650 (DKS Co. Ltd., Effective concentration: 26%) was used as thecationic urethane resin (D) as shown in Table 1.

Examples 16 to 21

Test plates were prepared as in Example 1 except that the above coldrolled steel plate or hot-rolled steel plates were used as a metal basematerial, and KBM-603 (N-2(aminoethyl)3-aminopropyltrimethoxysilane,effective concentration 100%, Shin-Etsu Chemical Co., Ltd.) or KBM-903(3-aminopropyltrimethoxysilane, effective concentration: 100%, Shin-EtsuChemical Co., Ltd.) was used as the silane coupling agent (B) as shownin Table 1, and the concentrations of the silane coupling agent (B) andthe cationic urethane resin (D) were as shown in Table 1.

Examples 22 to 25

Test plates were prepared as in Example 1 except that the concentrationof zirconium (A) was 500 ppm by masses, and the above cold-rolled steelplate or hot-rolled steel plates were used as a metal base material, andKBE-903 (3-aminopropyltriethoxysilane, effective concentration: 100%,Shin-Etsu Chemical Co., Ltd. or XS1003(N,N-bis[(3-(trimethoxysilyl)propyl)]ethylenediamine, effectiveconcentration: 50%, Nichibitrading Co., Ltd., Inc.) was used as thesilane coupling agent (B) as shown in Table 1, and the concentrations ofthe silane coupling agent (B) and the cationic urethane resin (D) wereas shown in Table 1.

Examples 26 to 37

Test plates were prepared as in Example 1 except that the above coldrolled steel plate or hot-rolled steel plates were used as a metal basematerial, and zinc nitrate (Zn) was used as an adhesiveness andcorrosion-resistance conferring material shown in Tables 1 and 2, andthe concentrations of zirconium (A), the silane coupling agent (B), andthe cationic urethane resin (D) were as shown in Tables 1 and 2.

Examples 38 to 41

Test plates were prepared as in Example 1 except that the above coldrolled steel plate or hot-rolled steel plates were used as a metal basematerial as shown in Table 2, and the concentrations of the silanecoupling agent (B) and the cationic urethane resin (D) were as shown inTable 2.

Comparative Examples 1 to 8

Test plates were prepared as in Example 1 except that the above coldrolled steel plate or hot-rolled steel plates were used as a metal basematerial as shown in Table 2, and the concentration of the silanecoupling agent (B) or the cationic urethane resin (D) was as shown inTable 2.

Reference Example 1

A test plate was prepared as in Example 1 except that a chemicalconversion treatment agent was prepared without including the cationicurethane resin (D) in the chemical conversion treatment agent.

Reference Examples 2 and 3

Test plates were prepared as in Example 1 except that the above coldrolled steel plate or hot-rolled steel plates were used as a metal basematerial, and surface conditioning was performed with Surffine GL1(Nippon Paint Surf Chemicals Co., Ltd.) at room temperature for 30seconds after post-degreasing water-washing treatment, and then chemicalconversion treatment was performed by dipping treatment using SurfdineSD-6350 (a zinc phosphate-based chemical conversion treatment agent fromNippon Paint Surf Chemicals Co., Ltd.) at 35° C. for 2 minutes insteadof using the above chemical conversion treatment agents as shown inTable 2.

The following evaluation tests were performed for the test platesobtained as described above from Examples 1 to 41, Comparative Examples1 to 8, and Reference Examples 1 to 3.

[Secondary Adhesiveness tests (SDT)] The resulting test plates were eachnicked deep enough to reach an underlying material along two paralleland longitudinal lines, and then dipped under a 5% NaCl aqueous solutionat 50° C. for 480 hours. Subsequently, a cut portion was exfoliated offwith a tape, and the exfoliation state of a coating material wasobserved. The exfoliation state was evaluated in accordance with thefollowing evaluation criteria, and an evaluation score of 2 or more wasconsidered as acceptable. The results were shown in Tables 1 and 2.

1: Not exfoliated2: Somewhat exfoliated3: Exfoliation width is 3 mm or more

[Salt-water spray tests (SST)] The resulting test plates were eachcross-cut deep enough to reach an underlying material, and continuouslysprayed with a 5% NaCl aqueous solution for 240 hours in a salt-waterspry test chamber maintained at 35° C. Subsequently, the width of ablister from a cut portion was measured. Those having a blister widthcomparable to or less than that in a case where a zinc phosphate-basedsurface treatment agent was used as shown in Reference Examples 2, 3were considered as acceptable. The results were shown in Tables 1 and 2.

[Combined cyclic corrosion tests (CCT)] The resulting test plates wereeach cross-cut deep enough to reach an underlying material, and thencombined cyclic corrosion tests were performed. Combined tests wereperformed for 100 cycles by a test method in accordance with JASOM609-91. After the tests, the width of a blister from a cut portion wasmeasured. Those having a blister width comparable to or less than thatin a case where a zinc phosphate-based surface treatment agent was usedas shown in Reference Examples 2, 3 were considered as acceptable. Theresults were shown in Tables 1 and 2.

TABLE 1 Silane Cationic Adhesiveness and coupling urethane corrosion-agent(B) resin(D) resistance Silane Silane Zirconium conferring agentcoupling coupling concentration(A) Concentration agent agent (ppm) Types(ppm) Types (ppm) Types (ppm) Examples 1 100 None 0 KBM-603 100 F2667D100 2 100 None 0 KBM-603 100 100 3 100 None 0 KBM-603 100 100 4 100 None0 KBM-603 100 100 5 100 None 0 KBM-603 100 100 6 100 None 0 KBM-603 100100 7 100 None 0 KBM-603 100 100 8 100 None 0 KBM-603 1 1 9 100 None 0KBM-603 1 1 10 100 None 0 KBM-603 5 5 11 100 None 0 KBM-603 5 5 12 100None 0 KBM-603 50 50 13 100 None 0 KBM-603 50 50 14 100 None 0 KBM-603100 Superflex 100 620 15 100 None 0 KBM-603 100 Superflex 100 650 16 100None 0 KBM-603 1 F2667D 5000 17 100 None 0 KBM-603 1 5000 18 100 None 0KBM-903 5000 1 19 100 None 0 KBM-903 5000 1 20 100 None 0 KBM-603 50005000 21 100 None 0 KBM-603 5000 5000 22 500 None 0 χS-1003 100 100 23500 None 0 XS-1003 100 100 24 500 None 0 KBE-903 5000 5000 25 500 None 0KBE-903 5000 5000 26 100 Zn 500 KBM-603 100 100 27 100 Zn 500 KBM-603100 100 28 20 Zn 500 KBM-603 400 400 Film Base amount SST CCT ((B)/(D))material (mg/m²) Coating SDT (mm) (mm) Examples 1 1 SPC270 13.4Powernics1010F 1 1.5 6.9 2 1 SPC780 26.6 1 1.7 7.3 3 1 SPH270 17.6 1 1.75.1 4 1 SPH440 21.8 1 2.0 7.2 5 1 SPH590 25.3 1 1.9 9.9 6 1 GA270 15.5 10.8 0.3 7 1 AL(6000series) 10.2 1 0.2 0.2 8 1 SPC270 23.4 2 1.8 8.7 9 1SPH270 25.5 2 2.1 9.9 10 1 SPC270 19.3 2 2.0 8.9 11 1 SPH270 22.2 2 2.29.2 12 1 SPC270 14.7 1 1.8 7.3 13 1 SPH270 16.2 1 1.6 6.5 14 1 SPH27015.9 1 2.0 7.4 15 1 SPH270 18.4 1 2.2 7.6 16 0.0002 SPC270 13.4 1 1.57.0 17 0.0002 SPH270 16.9 1 1.6 5.3 18 5000 SPC270 11.1 1 1.4 6.8 195000 SPH270 16.8 1 1.5 5.8 20 1 SPC270 9.5 1 1.8 8.3 21 1 SPH270 10.1 11.7 7.2 22 1 SPC270 38.5 1 1.5 6.8 23 1 SPH270 40.8 1 1.6 5.0 24 1SPC270 10.5 1 1.4 7.4 25 1 SPH270 15.3 1 1.5 6.6 26 1 SPC270 13.6 1 1.35.3 27 1 SPH270 17.2 1 1.3 4.9 28 1 SPC270 10.3 1 1.8 6.9

TABLE 2 Silane Cationic Adhesiveness and coupling urethane corrosion-agent(B) resin(D) resistance Solid Solid Zirconium conferring agentcontent content concentra- Concen- concen- concen- Film tion(A) trationtration tration ((B)/ Base amount SST CCT (ppm) Types (ppm) Types (ppm)Types (ppm) (D)) material (mg/m²) Coating SDT (mm) (mm) Exam- 29 20 Zn500 KBM-603 400 F2667D 400 1 SPH270 11.2 Powernics 1 1.9 7.1 ples 3010000 Zn 500 KBM-603 400 400 1 SPC270 18.4 310 1 2.2 8.3 31 10000 Zn 500KBM-603 400 400 1 SPH270 20.3 1 2.1 8.8 32 200 Zn 500 KBM-603 400 400 1SPC270 15.2 1 1.3 4.7 33 200 Zn 500 KBM-603 400 400 1 SPH270 19.7 1 1.64.5 34 200 Zn 500 KBM-603 200 400 0.5 SPC270 16.8 1 0.9 4.9 35 200 Zn500 KBM-603 200 400 0.5 SPH270 21.2 1 0.9 5.0 36 200 Zn 500 KBM-603 400200 2 SPC270 15.5 1 1.3 4.9 37 200 Zn 500 KBM-603 400 200 2 SPH270 20.21 0.9 5.0 38 100 None 0 KBM-603 1 100 0.01 SPC270 15.6 2 2.1 8.8 39 100None 0 KBM-603 1 100 0.01 SPH270 16.3 2 2.0 9.1 40 100 None 0 KBM-603100 1 100 SPC270 16.2 1 2.1 7.1 41 100 None 0 KBM-603 100 1 100 SPH27017.8 1 2.0 11.0 Compar- 1 100 None 0 KBM-603 0 F2667D 100 — SPC270 22.7Powernics 3 2.1 10.5 ative 2 100 None 0 KBM-603 0 100 — SPC780 28.5 3103 2.3 11.9 Exam- 3 100 None 0 KBM-603 0 100 — SPH270 26.4 3 2.4 11.9ples 4 100 None 0 KBM-603 0 100 — SPH440 30.3 3 2.2 15.3 5 100 None 0KBM-603 0 100 — SPH590 34.1 3 2.5 14.2 6 100 None 0 KBM-603 100 0 —SPH270 21.4 1 2.0 13.5 7 100 None 0 KBM-603 0 5000 — SPC270 18.7 3 1.910.1 8 100 None 0 KBM-603 0 5000 — SPH270 22.1 3 2.0 14.3 Reference 1100 None 0 KBM-603 100 F2667D 0 — SPC270 18.7 Powernics 1 2.0 7.1Example 2 Zinc phosphate treatment SPC270 2100 310 2 2.3 9.2 3 SPH2702500 2 2.5 11.3

Comparison of Examples 1 to 41 with Comparative Examples 1 to 5, 7, and8 shows that the metal base materials treated by the chemical conversiontreatment agents from Examples 1 to 41 have superior secondaryadhesiveness (SDT) as compared with the metal base materials treated bythe chemical conversion treatment agents from Comparative Examples 1 to5, 7, and 8. These results demonstrate that inclusion of the at leastone (B) selected from the group consisting of an amino group-containingsilane coupling agent, hydrolysates thereof, and polymers thereof in achemical conversion treatment agent can confer preferred post-coatingcorrosion resistance on a metal base material treated by the chemicalconversion treatment agent. Further, neither the metal base materialstreated with the chemical conversion treatment agents from ComparativeExamples 1 and 3 nor the metal base materials treated with the chemicalconversion treatment agents from Comparative Examples 7 and 8 showpreferred secondary adhesiveness (SDT). This indicates that an increasedcontent of the cationic urethane resin (D) can not provide preferredresults when a chemical conversion treatment agent does not contain theat least one (B) selected from the group consisting of an aminogroup-containing silane coupling agent, hydrolysates thereof, andpolymers thereof, and also indicates that preferred post-coatingcorrosion resistance can be conferred on a metal base material bypre-coating treatment of the metal base material with a chemicalconversion treatment agent including the at least one (B) selected fromthe group consisting of an amino group-containing silane coupling agent,hydrolysates thereof, and polymers thereof in combination with thecationic urethane resin (D).

Comparison of Examples 1 to 41 with Comparative Example 6 shows that themetal base materials treated with the chemical conversion treatmentagents from Examples 1 to 41 have superior results from the combinedcyclic corrosion tests (CCT) as compared with the metal base materialtreated with the chemical conversion treatment agent from ComparativeExample 6. These results indicate that inclusion of the cationicurethane resin (D) in a chemical conversion treatment agent can conferpreferred post-coating corrosion resistance on a metal base materialtreated with the chemical conversion treatment agent.

Comparison of Examples 1 to 41 with Reference Examples 1 to 3 shows thatthe metal base materials treated with the chemical conversion treatmentagents from Examples 1 to 41 have comparable or superior results fromthe salt-water spray tests (SST), the combined cyclic corrosion tests(CCT) as compared with the metal base materials treated with thechemical conversion treatment agents from Reference Examples 1 to 3.These results indicate that the metal base materials treated with thechemical conversion treatment agents according to the embodiments of thepresent invention have comparable or superior post-coating corrosionresistance as compared with the metal base material treated by theconventional pre-coating treatment method used for a cold-rolled steelplate from the reference example 1 and the metal base materialssubjected to the conventional zinc phosphate treatment from ReferenceExamples 2 to 3.

Further, comparison of Examples 1 to 7 shows that the metal basematerials treated with the chemical conversion treatment agents fromExamples 1 to 7 each have preferred post-coating corrosion resistance.These results indicate that the chemical conversion treatment agentsaccording to the embodiments of the present invention can unsureexcellent post-coating corrosion resistance regardless of the types oftreatment targets.

1. A chemical conversion treatment agent, comprising: at least one (A)selected from the group consisting of zirconium, titanium, and hafnium;at least one (B) selected from the group consisting of an aminogroup-containing silane coupling agent, hydrolysates thereof, andpolymers thereof; fluorine (C); and a cationic urethane resin (D). 2.The chemical conversion treatment agent according to claim 1, whereinthe total content of (A) is 20 to 10000 ppm by mass in terms of metal,and pH is 1.5 to 6.5.
 3. The chemical conversion treatment agentaccording to claim 1, wherein the total content of (B) is 5 to 5000 ppmby mass in terms of a solid content concentration, and the content of(D) is 5 to 5000 ppm by mass in terms of a solid content concentration,and the solid content mass ratio ((B)/(D)) of (B) to (D) is 0.0002 to5000.
 4. The chemical conversion treatment agent according to claim 1,further comprising at least one adhesiveness and corrosionresistance-conferring agent selected from the group consisting ofmagnesium ions, zinc ions, calcium ions, aluminum ions, gallium ions,indium ions, and copper ions.
 5. A pre-coating treatment method,comprising: treating a target workpiece with the chemical conversiontreatment agent according to claim
 1. 6. A metal member treated by thepre-coating treatment method according to claim 5.